Vibration-assisted vat photopolymerization for pixelated-aliasing-free surface fabrication

Mask image projection-based vat photopolymerization(MIP-VPP)offers advantages like low cost,high resolution,and a wide material range,making it popular in industry and education.Recently,MIP-VPP employing liquid crystal displays(LCDs)has gained traction,increasingly replacing digital micromirror devices,particularly among hobbyists and in educational settings,and is now beginning to be used in industrial environments.However,LCD-based MIP-VPPsuffers from pronounced pixelated aliasing arising from LCD’s discrete image pixels and itsdirect-contact configuration in MIP-VPP machines,leading to rough surfaces on the 3D-printed parts.Here,we propose a vibration-assisted MIP-VPP method that utilizes a microscalevibration to uniformize the light intensity distribution of the LCD-based mask image on VPP’s building platform.By maintaining the same fabrication speed,our technique generates asmoother,non-pixelated mask image,reducing the roughness on flat surfaces and boundary segments of 3D-printed parts.Through light intensity modeling and simulation,we derived an optimal vibration pattern for LCD mask images,subsequently validated by experiments.We assessed the surface texture,boundary integrity,and dimensional accuracy of componentsproduced using the vibration-assisted approach.The notably smoother surfaces and improved boundary roughness enhance the printing quality of MIP-VPP,enabling its promisingapplications in sectors like the production of 3D-printed optical devices and others.

3D printing of hydroxyapatite/tricalcium phosphate scaffold with hierarchical porous structure for bone regeneration

Three-dimensional(3D)-printed scaffolds have attracted considerable attention in recent years as they provide a suitable environment for bone cell tissue regeneration and can be customized in shape.Among many other challenges,the material composition and geometric structure have major impacts on the performance of scaffolds.Hydroxyapatite and tricalcium phosphate(HA/TCP),as the major constituents of natural bone and teeth,possess attractive biological properties and are widely used in bone scaffold fabrication.Many fabrication methods have been investigated in attempts to achieve HA/TCP scaffolds with microporous structure enabling cell growth and nutrient transport.However,current 3D printing methods can only achieve the fabrication of HA/TCP scaffolds with certain range of microporous structure.To overcome this challenge,we developed a slurry-based microscale mask image projection stereolithography,allowing us to form a HA/TCP-based photocurable suspension with complex geometry including biomimetic features and hierarchical porosity.Here,the curing performance and physical properties of the HA/TCP suspension were investigated,and a circular movement process for the fabrication of highly viscous HA/TCP suspension was developed.Based on these investigations,the scaffold composition was optimized.We determined that a 30 wt%HA/TCP scaffold with biomimetic hierarchical structure exhibited superior mechanical properties and porosity.Cell proliferation was investigated in vitro,and the surgery was conducted in a nude mouse in vivo model of long bone with cranial neural crest cells and bone marrow mesenchymal stem cells.The results showed our 3D-printed HA/TCP scaffold with biomimetic hierarchical structure is biocompatible and has sufficient mechanical strength for surgery.

A COMPLETE CHARACTERIZATION OF THE ROBUST ISOLATED CALMNESS OF NUCLEAR NORM REGULARIZED CONVEX OPTIMIZATION PROBLEMS

In this paper, we provide a complete characterization of the robust isolated calmness of the Karush-Kuhn-Tucker （KKT） solution mapping for convex constrained optimization problems regularized by the nuclear norm function. This study is motivated by the recent work in [8], where the authors show that under the Robinson constraint qualification at a local optimal solution, the KKT solution mapping for a wide class of conic programming problems is robustly isolated calm if and only if both the second order sufficient condition （SOSC） and the strict Robinson constraint qualification （SRCQ） are satisfied. Based on the variational properties of the nuclear norm function and its conjugate, we establish the equivalence between the primal/dual SOSC and the dual/primal SRCQ. The derived results lead to several equivalent characterizations of the robust isolated calmness of the KKT solution mapping and add insights to the existing literature on the stability of nuclear norm regularized convex optimization problems.

An Integrated System-Oriented Model for the Interoperability of Multiple Emergency Response Agencies in Large-Scale Disasters: Implications for the Persian Gulf

Failures in complex technological systems could have multiple dire aftermaths, including many deaths and injuries. These events, such as nuclear accidents, pose serious threats and long-lasting health and environmental consequences to workers, the local public, and possibly the whole country and neighboring regions. Such failures,given interconnectivities and interdependencies, could also have spillover effects and threaten the integrity of other systems operating in the same area. There is an essential need for effective integration and interoperability among multiple emergency response agencies, possibly from different countries, in the case of an accident in a safetysensitive industry that causes the release of hazardous materials or contaminants. This article proposes a generic integrated system-oriented model to address this urgent need. It has been applied to the Persian Gulf area and its waters as a case study because of the existence of multiple co-located, safety-sensitive industries such as nuclear power generation, offshore oil and gas drilling, seawater desalination, and seafood harvesting. The Persian Gulf region and its ecosystems are highly vulnerable, and the countries around the Gulf are tightly interdependent, with an urgent need for cooperative emergency response planning. The Black Sea and other semiclosed, water-based ecosystems can also benefit from this model.